In Media Res. Latin for 'into the middle of things.'
Not every story has to start with a long, slow brain-dump of world-building to establish setting. Many modern readers will put the book down and walk away when you do that.
Instead, consider starting right in the middle of the action, working forwards as you slowly explain how things got here. Perhaps beginning so simply as somebody knocking on the door.
Drop your characters into the middle of things and run with it. Your stories will move faster and your readers will be drawn in, never to escape again.
We'll also talk about Character Backstories, World/Culture Backstories, Technology Backstories, and the Perils of Prequelitis.
This is a 201-level book, taking you from writing merely good novels to that place where you are turning a quarter of a million or more words into one long, engaging story that your fans just can't put down.
Be sure to read the entire Business For Breakfast books and see how it can help you improve your writing craft and up your publishing game.